Cockroaches can be carriers of various diseases because they are commonly found near waste deposits or in the kitchen, where food is present. Restaurants may also experience cockroach infestations. Cockroaches can measure over 50 cm (2 in) length, with tropical species tending to be larger than those found in other climates. Cockroaches have six legs, two antennae and some have wings. However, most winged cockroaches are not particularly adept at flying. Cockroaches emit unpleasant odors and may also produce sound. The Madagascar hissing cockroach is the most famous of these vocal cockroaches, although more common species may produce quieter clicking or chirping noises.
It is popularly suggested that cockroaches will "inherit the earth" if humanity destroys itself in a nuclear war. Cockroaches do indeed have a much higher radiation resistance than vertebrates, with the lethal dose perhaps six to 15 times that for humans. However, they are not exceptionally radiation-resistant compared to other insects, such as the fruit fly.
Cockroaches are among the hardiest insects. Some species are capable of remaining active for a month without food and are able to survive on limited resources, such as the glue from the back of postage stamps. Some can go without air for 45 minutes. In one experiment, cockroaches were able to recover from being submerged underwater for half an hour. Japanese cockroach nymphs, which hibernate in cold winters, survived twelve hours at -5 degrees Celcius to -8 degrees celcius in laboratory experiments.
Experiments on decapitated specimens of several species of cockroach found a variety of behavioral functionality remained, including shock avoidance and escape behavior, although many insects other than cockroaches are also able to survive decapitation, and popular claims of the longevity of headless cockroaches do not appear to be based on published research. The severed head is able to survive and wave its antennae for several hours, or longer when refrigerated and given nutrients.